Jacques Mattheij

Technology, Coding and Business

Drastically Reducing Our Powerbill

Since the outbreak of the war in Ukraine the price of gas and electric power in the European Union has gone up enormously. Russia, a major supplier of gas to the EU has been sanctioned heavily, buying natural gas from Russia effectively pays for them to wage war on Ukraine and the price of electricity is tied to the price of natural gas, which has been going up and down like a jo-jo, but far more up than down. Not all countries are equally affected by this, countries that have a large proportion of hydro power and countries that have their own - and still usable - supplies of natural gas have an easier time to deal with this than countries that do not. The EU energy market - not the most transparent affair for mere mortals - which allows foreign suppliers access to the domestic markets can cushion some of these aspects but the difference in average price as well as the various means offered by governments to take the edge of for their citizens vary greatly, as do the individual contracts and the options offered by the various suppliers.

Ever since the beginnings of the COVID crisis we have worked from home, which means that all of the gear that used to sit in our offices is now here in the house and obviously that uses quite a bit of power. The house has four occupants, two adults, two teenagers and is about 200 square meters divided across three levels. The house has 25A x 3 phase 240V service and a natural gas line, which is used for both domestic hot water, some of the cooking (a hybrid gas/electrical stove) and the water based central heating system.

A typical setup in the Netherlands, where I live is that you have a network that serves your region and a choice of various suppliers. Once the price of energy started to go up faster than anticipated several of the suppliers here went bankrupt overnight, forcing their customers to re-negotiate with a different supplier at an entirely different rate. The practice effect is that for many households here since Jan. 1st 2022 the price of energy delivery has gone up tremendously, factors of five are not exceptional though in many cases - fortunately - it is still less than that and people that had the foresight to lock in their contracts prior to the outbreak of the war are sitting pretty, for a while at least.

Our household was not one of those, so when in August, after the annual adjustment we received the new tarifs it was bad. Our energy bill basically tripled overnight and roughly 1/3rd of my take-home salary would have gone towards the energy bill without some countermeasures. The plan we came up with was to create a mixture of savings measures and to install some generating capacity of our own, and to offset some of our heating requirements with an air-air heatpump that we already had but only used in airconditioning mode.

This house was built in the early 1970’s, it is not insulated all that well between the inner and the outer wall, and fixing that is a very expensive affair, both because of how the house was built as well as because there is already (bad) insulation in there. Removing the old insulation and replacing it with something better would be nice but from a cost-benefit perspective it is not the best investment right now (though we may still opt to do this in the future). What we could do fairly easily is to drop the temperature that the gas fired central heating system operates at. The default the heater was programmed to was 65 degrees Celsius, we dropped that to 45 degrees which had an immediate effect on the gas consumption. We also dropped the thermostat from a toasty 20 degrees to 18 degrees, which may not seem like much but the difference was very noticeable. Lower than that is not an option, for one humidity would become a problem, for another the house is very unevenly heated and 18 where the thermostat is can mean anywhere from 16 to 20 depending on where (how high up) you are in the house. But the every room has thermostatic valves on the radiators and those we adjusted to try to get the rooms as close to each other as possible temperature wise. Another thing we did was to change from using the front door of the house to using the backdoor, which does not sit next to the stairwell. This reduced the amount of air exchange every time someone came into or left the house. For myself, I have tried to take shorter showers, though I definitely miss them (joint issues). Together these simple measures shaved off more than half of our gas consumption.

On the electrical side there was a lot that could be done as well. First we made inventory of all of the consumers that we had, and decided whether or not we really needed them, if they could be replaced by something less power hungry if we did and if not if we could reduce our usage. We replaced all of the remaining halogen bulbs (we still had quite a few) with LEDs, in some cases this required some minor rewiring because not all of the power supplies for the halogen bulbs liked the LEDs but because they draw so much less power it was easy to move some of these to supplies that worked well. For some bulbs finding an LED replacement was quite tricky but in the end we found a way to get rid of all of them. Identifying consumers can be quite hard, we installed a ‘Smile P1’ interface to our distribution point to determine momentary power draw and flipped circuit breakers one-by-one until we had a reasonable insight into how much power each circuit was using. The worst consumers: my main computer (a beefy I7 with a very large amount of RAM and a 1080ti graphics card that I used for the machine learning portion of the Lego sorting machine), our NAS (a 12 bay Synology) and a domestic water heater in the kitchen (which took forever to find). The second fridge/freezer was switched off as well, and a whole slew of ghost loads was killed off by simply pulling the wall warts when the devices are not in use. My computer was replaced by an old laptop that I still had but did not use, it has a provision for dual monitors (besides the built in LCD) so I still have more or less the same setup as before, with just half the RAM. I did replace the rotating rust drive with an SSD, which was surprisingly affordable given the capacity.

All of these changes together cut our monthly consumption from about 800 KWh on average (which is insane) to a much more reasonable 270 KWh. And the solar panels completely offset that during the month of October. Another batch of 10 panels will arrive next week, which will allow us to heat part of the second floor using an air-conditioner run in reverse (a split air conditioning unit is essentially just a heatpump and you can run those in reverse). This should further reduce the gas bill.

When we bought this house it had 16 solar panels installed, but we had to take those down to modify the attic space. The plan always was to put them back up once that work was done but we had simply not gotten around to it yet, just prior to removing them the inverter broke and since the start of the war in Ukraine the availability of solar panels and inverters is quite bad, lead times are several months. After searching on the local equivalent of Ebay I found one party that still had a slightly older model inverter sitting around, a 3 Phase 4KW unit that they somehow never sold. I don’t particularly care for the latest and greatest in inverters so I was happy to take it off their hands at a bit of a discount. When it arrived it turned out the inverter had been dropped, and quite badly, the casing was cracked, the DC disconnect had been bent out of shape and a bolt had broken out of the cast aluminum housing. It must have taken quite a fall given the amount of foam that the inverter came packed in, weirdly enough the cardboard box was fine though it did look as if the inverter had been re-packed at least once before (judging by the amount of packing tape on the box). I contacted the company and they were super reasonable about it, they offered me to either take it back for a full refund or a 50% discount if I wanted to keep it. I’m not afraid of power electronics, wired up a test installation and inspected the inverter mechanically, it worked in spite of the damage and did not get overly hot or let out any magic smoke, so I took the discount. This allowed me to re-install the 16 panels that I had before on the roof of our garage.

I then ordered another batch of panels, much more modern (the other ones are about a decade old, 265 Watts each), 400 W AEG units that I found a reliable supplier for and went to pick them up, then installed those on a covered area outside in the garden. 10 of those comes to 4000 Watts installed power, plus the 16 265 Watt ones, another 4250 Watts (but given their age I would derate those to probably closer to 200 Watts today, so say 3200 Watt). Adding all of that up gives you a bit over 7000 Watts in installed power, much more than the inverter could handle. Another trip through the second hand listings and I found a single phase unit that will do 3000 Watt. The panels are mounted flat on the garage and lean-to roofs, so that’s a double penalty, first there is the problem of the angle at which the sun shines on those panels, and second the houses here will shade the panels during part of the day. But it makes a nice bit of power,

From an initial 1500 euros / month we are now down to about 350 euros ex government rebates, and that is in the bad part of the year. Obviously, December, the worst month for solar is still to come and I definitely don’t expect miracles, but as long as we still have net-metering here (until Dec 2024 at a minimum) we can compensate for that during the summer. The total cost of the installation was about 10K, which I expect - assuming prices remain steady - to pay for itself in less than four years. Clearly, the energy savings are a major factor in the whole picture, without that the effect of the solar installation would be far less. But the two combined meant that for October our electricity usage relative to the grid was negative, resulting in a portion of our gas usage being offset by electricty over production.

There are some things that helped which may make this hard to replicate: the first, and most obvious one is that we had enough savings to make all of this happen on short notice. we also had a lot of surface area to play with, 60 square meters of flat roof which is now completely covered with panels, and another 30 square meters higher up on the roof of the house which will soon be covered as well. Not every location has such a large amount of usable roof area. The second factor is that even though there is some shading we don’t have any really high buildings nearby that shades the whole installation. Mounting panels flat is not ideal, for one they make less power than when they are properly ‘aimed’, for another they can easily foul up (leaves, bird droppings and so on). But even if the panels are positioned less than ideal, are partially shaded and need periodic cleaning (or are simply not perfectly clean) the sheer quantity of them means that even of the whole setup is operating at 10% efficiency it still handily outstrips our usage during the day with the sun this low in the sky. Once we’re past the solstice it will get better day-by-day and during February and March (when we consumed the most gas in other years) I expect to be able to use the air-air heatpump for heating purposes a lot. Finally, not everybody is able to adjust the temperature just like that, if you have health issues or if your house is even more humid than this one you may have to keep up the heat just to avoid ending up with fungi or damage. But even then a critical look at your power consumption may help identify some areas where you can save.

I hope this article will help someone looking to do something similar, if you have questions or feedback feel free to reach out to jacques@modularcompany.com.